FOXO1 ChIP-seq was performed as before with minor modifications (Lin et al., 2010). Briefly, 3 x 107 T cells were fixed for 5 to 10 minutes at room temp in 1% formaldehyde then resuspended in lysis buffer. Following adaptor ligation, the DNAs were size selected (200-300bp) by 8% PAGE and index primers added by PCR. Samples were purified by 8% PAGE and precipitated with ethanol.